Expectations?

One of the 4th edition campaigns I am running started with the first module for this editions, H1-Keep on the Shadowfell. Since I started with this module and have a few maps in the DM's guide I decided to continue using the maps and locations provided, I have re-created the map provided in the DM's guide Soon to be posted here. I did add my own twist with an overarching storyline that is supposed to get the characters involved.

Edit: Here is a link to the map that I made from the one provided in the DM's Guide.
Winterhaven and surroundings


You see a couple of centuries ago an oracle just spouted out an epic, as oracles sometimes do. In the epic it was described that the royal family was destined to be the end of Orcus, or at least banish him for a millenia. That epic lists out where the hero is expected to go, what he is expected to use and how he is supposed to end Orcus' reign.

Here are some stanzas that the players have already discovered:

From the past, the future's written
Of the blood of ancient kings
They shall be Orcus' destroyer
Through powerful prismatic rings

In their path, shadows fallen
His death, black and painful fated
By his master, unlife granted
until his soul's hunger sated

Mountain's protectors have the answer
To travel the path of glory
Forged by their ancestral spirit
A ring begins the blood's story

Before ancient Shadow's Pillars
Beneath the shadow darkened sun
With heartening strikes on Orcus
The cleansing war has begun

Bright now is their shadowed future
Strengthened by the coming sun
Fear and horror reduced to nothing
In the end the battle is won

Part of the story is a mercenary company that was hired to guard the royal family until the prophecy came to pass. Red Mithril stayed with the family wherever they went, unfortunately There was an incident at the Keep on the Shadowfell that broke up the mercenary company and scattered the few remaining members of the family.

Assuming the characters find all the information they need, what do you think the chances are that the campaign will go as expected?